If you are interested in getting some extra worldbuilding for the Witchlands and want an origin story for Ryber, then I would recommend picking this up. The book uses letters and documents intermittently to drive the narrative, so it gives you some introspection into different characters. The pacing is slow since there is so much focus on going back and forth between the past and the present and the world building. I would not go into this expecting a lot of adventure and plot. It's mostly an adjunct to the main series to give more context to the world and character development for Ryber specifically. It was incredible to see what her upbringing was like with the Sightwitches and how much she has grown and changed since then. I have not read Bloodwitch yet, and Witchshadow has not been published. However, I follow Susan Dennard online and she noted that some of the future books will be hinging a bit more on this installment. When I read them I'll be able to more accurately determine how necessary it is to actually read this. Overall, a solid side book, but not one that I think everyone will necessarily enjoy reading.